As the Home Secretary set out in his evidence to the Home Affairs Select Committee on 23 May 2006, no Government have been able to produce an accurate figure for the number of people who are in the country illegally, and that remains the case.
The Organisation for Economic Co-operation and Development (OECD) has published estimates for the sizes of the unauthorised migrant population for a selection of other countries in Europe on their website at: http://www.oecd.org. The following table is taken from the ‘International Migration Outlook’ publication.
International Migration Outlook—ISBN_92-64-03627-X-©_OECD_2006—Part 1
Number Percentage of total Method of estimation 2005 Australia 50,000 0.2 Double card system 2005 Japan 210,000 0.2 Double card system 2004 (18) United States 10,300,000 3.6 Residual method 2004 Netherlands 125,000-230,000 0.8-1.4 Capture/recapture 2005 Switzerland 80,000-100,000 1.1-1.5 Delphi method 2005 (4) Spain 690,000 1.6 Regularisation 2002 (4) Italy 700,000 1.2 Regularisation 2001 (6) Portugal 185,000 1.8 Regularisation 2001 (3) Greece 370,000 3.4 Regularisation Note: The number in parentheses indicates the number of years since the previous major regularisation. The regularisation numbers cover only persons applying and thus are a lower bound for the number of unauthorised immigrants. Sources: Australia, Japan, southern European countries: national SOPEMI reports. United States: Van Hook, Bean and Passel 2005. Netherlands: Snel et al. 2005. Switzerland: GFS 2005.